Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$168.43	13.359%	$190.9306	$190.93	$190.95	$190.90
Purchase #2	$27.92	7.257%	$29.9462	$29.95	$29.95	$29.90
Purchase #3	$138.90	3.337%	$143.5351	$143.54	$143.55	$143.50
Purchase #4	$19.94	3.236%	$20.5853	$20.59	$20.60	$20.60
Purchase #5	$61.65	10.848%	$68.3378	$68.34	$68.35	$68.30
Purchase #6	$50.85	3.179%	$52.4665	$52.47	$52.45	$52.50
Purchase #7	$184.84	8.330%	$200.2372	$200.24	$200.25	$200.20
7 purchase totals =	$652.53		$706.0387	$706.06	$706.10	$705.90